The EZ deflaters were created by Currie Enterprises. The very first ones were very expensive. When Currie outsourced them to off shore manufacturing it made them affordable and also opened up knock offs to the masses. The concept in ingenious and very simple. Screw the apparatus on the valve stem. Push the knob into the valve stem and remove it internally. Slide the large knob to open the open ports. Let the tire air down to where you want it then simply close the air ports, then screw the valve stem back into place that is out but still contained in the apparatus. Unscrew the assembly and move on.....no chance of lost valve cores.